Current regulating device



Feb. 16,` 1932. H. M.. sTEPHENsoN 1,845,973

CURRENT REGULATING DEVICE Filed Nov. 5, 1928 Hugh M Stepheson,

bg Mm y-lis AttQr-eg.

Patented Feld. is, 1932 UNITED STATES PATENT OFFICE HUGHM. 'STEPHENSOIL 0F FORT WAYNE INDIANA, ASSIGNOR TO GENERAL HIECTBIG COMPANY, A CORPORATION OF NEW YORK cUnnENT amULA'iiNGinEvicE lApplication led November 5, 1928. Serial No. 817,232.

My invention relates to current regulating devices, moi'e particularly to variable resist? ances or rheostats in which the amount of resistance is varied by altering the compres- @j sion ofv a resistance member through which the current is caused to flow, and has for its object an improved construction in'a device of this character.

My invention has particular ada tation Il when embodied in rheostats suitable or controlling motors for sewing machines or similar light duty service especially in those rheostats which are controlled by the foot or the knee of the operator.

Among the advantageous features afforded by m invention are improved supporting means or the resistance members, an improved casing within which the resistances and the actuating means are enclosed as well as improved means for mounting the rheo- Stat. Aa, l l

In carrying out l'my invention I have p rovided a casing enclosing a pair of insulating members, one of these members being fixed and the other member, movable toward or away .from the fixed member, and a compressible resistance unit supported on the movable member between this member and the fixed member. I have also provided resilient $0 means between the resistance unit and the fixed member for biasing the unit'ltoward the movable member, and an actuating member for forcing the movable member and resistance unit toward the fixed member against the action of the resilient means.

For a better understanding of my invention, reference may be had to the accompanying drawings in which Fig. lis a perspective view of a rheostat embodying my invention; Fig. 2 is a side elevation; Fig. 3 is a sectional view taken on the line- 3-3 of Fig. 2; Figv 4 is a perspective view of the actuating arm,

while Fig. 5 is an elevation partly in sectionv illustrating the mounting of the rheostat.

Referring to the drawings` in carrying out my invention in one form I have provided a.A

rheostat in which the resistances and the actuating mechanism therefor are enclosed within a casing 1()`ormed of a pair of sheet metal stampingsll and 12 so shaped that the casing has the 4form of a letter lL. The member 11 of the casing is formed preferably from@ bent into the shape of a letter L and is of a size sufiicient to form a covering for the portion 11 of the casing. The member 12 is provided, preferably by stamping, with a plurality of apertures 14 for the purpose of dissipating heat generated in the resistance units. The side members 13, 13 are provided with rolled edges forminggrooves 15, 15 and it will be observed with reference to Fig. 1 that the cover. member 12 is clamped in place between these grooves. l

I have provided a pair of compressible resistance units 17 and 18 supported between a fixed insulating member 19 and a movable insulating member 20. The resistance units 17, 18 are preferably formed of a plurality of small disks or plates of carbon or a. suitable carbon compound, each of the resistance units thus constituting a so-called carbon pile. The pro erty of a resistance unit of this type where y its electrical resistance is decreased upon compressing together the disks or plates forming the uniit, is well known.

The insulating members 19 and 20 are preierably formed of a suitable heat resisting in' sulating material such as porcelain and are shaped so that the member 2() may be telescoped within the member 19, the latter member being provided with an enlarged recess 21 into which lthe member 20 is adapted to be moved.

The insulating member 20, as will be observed with reference, more particularly to Fig. 3', has the shape of an inverted letter T, the-vertical portion of this member extending within the recess 21 of the fixed insulating member 19. The vertical portion of the member 2O is not as Wide as the recess 2.1. and thus spaces are formed at the sides between the vertical portion and the sides of the recess 21, these spaces being substantially filled by the resistance units 17 18. The horizon` tal portion of the insulating member 20has a width slightly smaller than the width of:

the vaperture 21 so that the member 20 may slide in and out of thefixed insulating member 19, while still substantially closing the I 5 opening formed by the recess 21. j

The resistance units 17 and 18 rest upon metallic disks 22, 23 which in turnare secured to the insulating member 2O by means of suitable screws 24, 25, the screws serving as terminals whereby electrical connections may be made to the resistance units 17, 18. A pair of metallic disks 26, 27 provided with projections 28, 29 rest upon thel upper ends of the resistance units 17 and 18. Aiiat leaf spring 3() in the shape of a bow rests upon the projections 28 and 29 of the metallic disks 26, 27 and at its upper side engages the fixed insulating member 19. 'A helical compression spring 31 is supported between the 'insulating 2o members 19 and 20, being mounted in an aperture provided for this purpose in the vertical portion of the insulating member 20.

' -The fixed insulating member 19 is provided with an aperture 32 extending horizontally 25 through the upper part of the member 19.

The aperture 32 is substantially oval in sectionl and serves to hold a tubular metallic Fmember 33 having a depending tab 34. The ends of the tubular member 33 are threaded 30 to contain machine screws 35, 36 which are passed through the side portions 13 of they casing member 11. It will be observed that the depending tab 34 on the tubular member 33 projects into the lower portion of the oval- 95 shaped aperture 32 and prevents the tubular member 33 from turning within this aperture while the screws 35, 36 are being threaded into or out of the member 33. In order to limit the movement of the member 20 and to prevent disassembly or disarrangement of the parts of the resistance units, the member '20 is provided with a transverse slot 37 and.

the xed insulating member 19 has secured therein a rivet' 38 extending into the slot 37.

It will thus be seen lthat the movement of the member 20 relative to the fixed member 19 is limited to the length of the slot ,37. c

. In order vto force the movable insulating member 2O andthe resistance units 17,18 into the fixed insulating member 19 against the compression of the springs 30 and 31, I have provided an actuating arm 40 shown more clearly in Figs. 2 and 4. The arm 40 has formed at one end an outwardly projecting,

rectangularly shaped portion 41 and at the other end a tab 42 bent upwardly at right angles to the arm 40. Between its two ends the arm 40 is provided with an upward bend 43 forming agroove in the under sid@ of the arm 40, this groove serving-as a bearing on a rod 44 secured in the casing 10 between the Iside portions 13 of the casing membery 11.

- .The tab 42 of the arm 40 is adapted to en- "gage a recess 45 in the lower surface of the movable insulating member 20. It will be :temeva observed with reference more particularly to Fig. 1.that the two portions 11 and 12 of the l casing 10 do not meet at the outer orrighthand end of the rheostat and an aperture 46 is thus formed through which the outwardly projecting .portion 41 of the arm 40 extends. The member 12 of the casing 10 is provided with a pair of openings 48, 49 and the arm 40 with a pair of openings 50, 51, the latter openings being so located as to be directly under the openings 48, 49 in the casing member 11 so that screws may be inserted downwardly through the openings 48, 50 and 49, 51 respectively and through apertures 51a, only one of which is shown, in the bottom of the casing 10 in order to secure the casing to a suitable support suchl as the framework of a sewing machine. The bottom of the casing 10 is provided at the rear or left-hand end, as in viewf ing F ig. 2, with a pair of projecting caps 52 85 and 53 and at the front or right-hand end with a pair of resilient `members 54, preferably of rubber. The projecting caps 52, 53, are adapted to be removed in order to facilitate the connection of the electrical conductors to screws 24 and 25, and afterl being replaced serve in` conjunction with the members 54 as supporting feet for the rheostat. An .apery ture 55 is provided in each of the side portions 13 to allow for the insertion of a resilient insulating bushing 55a which 'is sleeved over the electrical conductor 56 attached to the terminals 24, 25 of the resistance units 17, 18,

' the two apertures 55, 55 being provided'to allow for right or left hand assembly of the electrical connections. The resilient foot members 54 and the insulating bushing *55al are preferably ident-ical in construction, these members being described and claimed in the' copending application of Marvin L. Norris, Serial Number 198,855, assigned to the saine assignee; as this invention. The above identiied' application is a division of another c opending application of Marvin L. Norrls, Serial Number 98,879, also assigned to the same assignee as this invention. vAn aperture 57 shown in Fig.'v 5 is provided in the bottom n ofthe casing 10 at a point substantially at the center of the rear or lower left-hand edge' of the casing, this aperture constituting a s crewslot enabling the bottom wall of the caslng to be slid under thehead of a screw 58 which may be-inserted in the frame or support to which the rheostat is to be attached. The aperture 57 is formed by punching in a small portion of the metal forming the bottom wall of the casing 10, this punched-in portion being then bent upwardly to partly surround v and form a supporting tab 59 for the conducf tor 56, as is shown clearly in Fig. 5. When it is desired to mount the rheostat on a supporting member such for instance as the framework of a sewing machine, the bottom wall of the casing is pushed under the head of the screw 58 which has preferably been 130 vss screwed for part of its length into the supporting framework, care having been taken that-sufficient room is left under the head of the screw to allow for the insertion thereunder ofthe bottom wall of the casing 10, as is clearly shown in Fig. 5. Additional screws, notl shown, are then inserted through the apertures 48, 49, 50, 5l, 51a, 51a and screwed into the supporting framework, the heads of thescrews engaging the bottom wall of the casing around the' apertures 51a, 51a.

The outwardly proJecting ortion 41 of the arm 40 is provided with t ireaded apertures 60 and it is contemplated that if or when the-rheostat is to be used for knee operation, a suitable knee-engaging member, not shown, will be attached to the portion 41 by means of screws threaded linto the apertures 60. W'hen the rheostat is used for foot operation, .it will be placed preferably on the floor and the foot of the operator will directly engage the outwardly projecting portion 41.

ln operation, my rheostat preferably is at- .tached to the frame or cabinet of a Sewing machine or the like, if knee operation is desired, or to the floor if it be desired to actuate the rheostat by the foot of the operator. The operator, by pressing on the outwardly projecting portion 41 of the arm 40, either ingmember as hereinbefore described, or directly by the foot, causes the arm to move about the shaft 44, whereupon the rear end of the arm 40 forces the, movable insulating member 20 into the recess 21. against the compression of spring 31. The resistance units 17, 18 will be forced against the iiat spring 30 and the carbon disks or plates of the resistance members will thus be compressed. A slight slip or wiping action will loccur between the spring 21 and the projections 2S, 2% of the metallic members 26, 27 thereby insuring a good electrical contact between the ends of the resistance units 17. 1li and the spring 21. The resistance units '17, 18 are thus connected in series in the circuit to be contrciled, the spring 21 serving both as means for electrically connecting the resistance units in series and as a bias for returning the resistance units to their starting position. The operator by exerting a greater or lesser pressure on the arm 4d will lcause 'the resistance of the units 17, 18 to motor to be governed will. be varied .accordingly.

While I have described my invention as embodied in concrete form and operating inv through the medium of a suitable knee-engagbe decreased or increased and the speed of the invention, the scope of which `is set forth in the annexed claims.

What I claim as new and desire to secure by Letters Patent o f the United States, is:

1. A rheostat comprising an L shaped casing, an insulating member'tixedly mounted in one branch of said casing, said fixed member being provided with a recess, a second insulating member slidabl mounted within said recess, a compressi le resistance unit mounted. in said recess, one end vof said unit being supported upon said slidable member, a spring between the other end of said unit and said fixed member, and an actuating arm for said slidable member, said arm being pivotalqly mounted within the other branch of said casing.

2. A rheostat 'comprising a casing, a member made of electrically insulating material secured in said casing, said member being provided with a` recess, a secondmember` made of electrically insulating material slidably mounted in said recess and loosely fitting therein, means for moving said second member in said recess toward and away from said first member, a pair of compressible-resistancey units in said recess mounted on opposite sides of said second member having their inner ends substantially ilush with the inner end of said second member, and resilient means between the inner ends of said members forming an electrical connection between the inner ends of said resistance units. In witness whereoLI have hereunto set my hand this 2nd day of November, 1928.

HUGH M. STEPHENSON. 

